Power supply circuit for motherboard

ABSTRACT

A power supply circuit for providing power and detecting a plurality of loads&#39; input voltages on a motherboard includes a pulse width modulation (PWM) controller, a voltage output circuit and a voltage feedback circuit electrically connected to the PWM controller and the plurality of loads. The PWM controller outputs PWM control signals. The voltage output circuit receives the PWM control signals and outputs working voltage to the plurality of loads according to the received PWM control signals. The voltage feedback circuit detects the plurality of loads&#39; input voltages and outputs feedback signals to the PWM controller according to the detected input voltages. The PWM controller adjusts its PWM control signal outputs, according to the received feedback signals, and adjusting working voltages to the plurality of loads.

BACKGROUND

1. Technical Field

The disclosure generally relates to power supply circuits, especially toa power supply circuit for motherboard with voltage feedback circuit.

2. Description of Related Art

With the rapid development of personal computers, development of highperformance components for computers have brought about a correspondingincrease in power use. A motherboard has a crucial effect on thestability of the computer. A power supply circuit is specially designedfor providing power to the motherboard. The typical power supply circuitdetects an input voltage of a load on the motherboard and adjusts itsvoltage output to the load according to the detected input voltage.However, the typical power supply circuit can only detect an inputvoltage of a single load at a time. When the power supply circuitprovides power to multiple loads on the motherboard, the power supplycircuit cannot detect input voltages of the multiple loads and adjustinput voltage for each of the multiple loads. Further, loads on themotherboard may cause digital errors and make the computer reboot.

Therefore there is a need for improvement in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the embodiments can be better understood with referencesto the following drawings. The components in the drawings are notnecessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the principles of the embodiments. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the several views.

FIG. 1 is a circuit diagram of an embodiment of a power supply circuitfor motherboard.

FIG. 2 is a circuit diagram of the voltage feedback circuit of FIG. 1.

FIG. 3 is a comparative graph showing signal waveforms of power-goodsignals, feedback signals, and input voltage signals of two loads on themotherboard.

DETAILED DESCRIPTION

The disclosure is illustrated by way of example and not by way oflimitation in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that referencesto “an” or “one” embodiment in this disclosure are not necessarily tothe same embodiment, and such references mean at least one.

Referring to FIG. 1, a power supply circuit for motherboard providespower and detects two loads 30 and 40 input voltages includes a pulsewidth modulation (PWM) controller U, a voltage output circuit 100 and avoltage feedback circuit 200 electrically connected to the PWMcontroller U and the loads 30, 40. The PWM controller U outputs PWMcontrol signals to the voltage output circuit 100. The voltage outputcircuit 100 outputs working voltages to the loads 30, 40 according tothe received PWM control signals. The voltage feedback circuit 200detects the loads 30, 40 input voltages respectively, and outputsfeedback signals to the PWM controller U according to the detected inputvoltages. The PWM controller U adjusts its PWM control signal outputsaccording to the received feedback signals, and adjusts working voltagesto the loads 30, 40.

The PWM controller U includes a boot terminal BOOT, an upper driveterminal UGATE, a phase terminal PHASE, a lower drive terminal LGATE, acompensation terminal COMP, a feedback terminal FB, a feedback groundterminal FBG and a power terminal VSEN. The voltage output circuit 100includes MOSFETs Q1 and Q2, capacitors C1, C2 and inductor L. The upperand lower drive terminals UGATE and LGATE are electrically connected tothe MOSFETs Q1 and Q2 grids respectively. A MOSFET Q1 drain receives aDC voltage VCC1. A MOSFET Q2 source is grounded. A MOSFET Q1 source anda MOSFET Q2 drain are grounded by the inductor L and capacitor C2connected in series. A connection point between the inductor L andcapacitor C2 outputs the working voltages. The boot terminal BOOT iselectrically connected to the phase terminal PHASE through the capacitorC1. The phase terminal PHASE is electrically connected to the MOSFET Q1source and the MOSFET Q2 drain respectively. The connection pointbetween the inductor L and capacitor C2 is grounded by the load 30, andis grounded through a switch S and the load 40 connected in series. Aconnection point between the switch S and the load 40 is grounded by acapacitor C3. In one embodiment, the MOSFETs Q1 and Q2 are N channelMOSFETs.

Referring to FIG. 2, the voltage feedback circuit 200 includes atransistor T, MOSFETs Q3 and Q4, Zener diode D and resistors R2˜R4. Atransistor T base is electrically connected to a diode D anode. A diodeD cathode receives a power-good signal PWRGD. A transistor T source isgrounded. A transistor T collector receives a DC voltage VCC2 throughthe resistor R2. The transistor T collector is electrically connected toa MOSFET Q3 grid. A MOSFET Q3 source is grounded. A MOSFET Q3 drainreceives the DC voltage VCC2 through the resistor R3. The MOSFET Q3drain is electrically connected to a MOSFET Q4 grid. A MOSFET Q4 sourceis grounded by the load 40. A MOSFET Q4 drain is grounded through theresistor R4 and load 30 connected in series. The MOSFET Q4 drain iselectrically connected to the feedback terminal FB through a resistorR1. In one embodiment, the transistor T is a NPN type transistor; theMOSFETs Q3 and Q4 are N channel MOSFETs.

In use, when the switch S turns off, the PWM controller U outputs PWMcontrol signals and controls the voltage output circuit 100 to provideworking voltage for the load 30. The power-good signal PWRGD is lowvoltage level. The transistor T turns off. The MOSFET Q3 turns on andthe MOSFET Q4 turns off. The load 30 input voltage is transmitted to thePWM controller U through the resistor R4. The PWM controller U adjustsits PWM control signal outputs, according to the received load 30 inputvoltage, and adjusts the working voltage to the load 30.

When the switch S turns on, the PWM controller U outputs PWM controlsignals and controls the voltage output circuit 100 to provide workingvoltages for the loads 30, 40. The power-good signal PWRGD is highvoltage level. The transistor T turns on. The MOSFET Q3 turns off, andthe MOSFET Q4 turns on. The load 30 input voltage is transmitted to thePWM controller U through the resistor R4. The load 40 input voltage istransmitted to the PWM controller U through the MOSFET Q4. The PWMcontroller U adjusts its PWM control signal outputs, according to thereceived loads 30 and 40 input voltages, and adjusts working voltages tothe loads 30, 40. A loads 30 and 40 input voltages receiving proportionis adjustable by changing a resistor R4 resistance, therefore the PWMcontrol signal adjusting strength is adjusted.

Referring to FIG. 3, an oscillographic is used to detect the power-goodsignal waveforms, feedback signals and the loads 30 and 40 input voltagesignals on a motherboard (not shown). Signal waveforms 300, 400, 500,600 are corresponding to the loads 30 and 40 input voltages, power-goodsignals and feedback signals respectively. In FIG. 3, when thepower-good signal PWRGD is low voltage level, the feedback signalwaveform 600 received by the PWM controller U overlapping the load 30input voltage signal waveform 300. When the power-good signal PWRGD ishigh voltage level, the feedback signal waveform 600 received by the PWMcontroller U is delayed for a short period and then overlaps the load 40input voltage signal waveform 400.

It is to be understood, however, that even though numerouscharacteristics and advantages have been set forth in the foregoingdescription of preferred embodiments, together with details of thestructures and functions of the preferred embodiments, the disclosure isillustrative only, and changes may be made in detail, especially inmatters of shape, size, and arrangement of parts within the principlesof the disclosure to the full extent indicated by the broad generalmeaning of the terms in which the appended claims are expressed.

What is claimed is:
 1. A power supply circuit for providing power anddetecting input voltages of a plurality of loads on a motherboard,comprising: a pulse width modulation (PWM) controller capable ofoutputting PWM control signals; the PWM controller comprises a firstdrive terminal, a phase terminal, a second drive terminal and a feedbackterminal; a voltage output circuit capable of receiving the PWM controlsignals and outputting working voltage to the plurality of loadsaccording to the received PWM control signals; the voltage outputcircuit comprises a first MOSFET and a second MOSFET; the first andsecond drive terminals are electrically connected to grids of the firstand second MOSFETs; a first MOSFET drain is capable of receiving a firstvoltage; a second MOSFET source is grounded; a first MOSFET source and asecond MOSFET drain are electrically connected to output workingvoltages; and the phase terminal is electrically connected to the firstMOSFET source and the second MOSFET drain; the plurality of loadscomprises a first load and a second load; the first MOSFET source andthe second MOSFET drain are electrically connected to each other andgrounded by the first load; and the first MOSFET source and the secondMOSFET drain are electrically connected and grounded through a switchand the second load that are connected in series; and a voltage feedbackcircuit electrically connected to the PWM controller and the pluralityof loads; wherein the voltage feedback circuit is capable of detectingthe input voltages of a plurality of loads and outputting feedbacksignals to the PWM controller according to the detected input voltages;and the PWM controller is capable of adjusting its PWM control signaloutputs, according to the received feedback signals, and adjustingworking voltages to the plurality of loads; the voltage feedback circuitcomprises a transistor, a third MOSFET and a fourth MOSFET; a transistorbase is capable of receiving a power-good signal; a transistor source isgrounded; a transistor collector is capable of receiving a secondvoltage through a first resistor; the transistor collector iselectrically connected to a third MOSFET grid; a third MOSFET source isgrounded; a third MOSFET drain is capable of receiving the secondvoltage through a second resistor; the third MOSFET drain iselectrically connected to a fourth MOSFET grid; a fourth MOSFET sourceis grounded by the second load; a fourth MOSFET drain is grounded by thefirst load; and the fourth MOSFET drain is electrically connected to thefeedback terminal.
 2. The power supply circuit of claim 1, wherein thePWM controller further comprises a boot terminal; and the boot terminalis electrically connected to the phase terminal through a capacitor. 3.The power supply circuit of claim 1, wherein the first and secondMOSFETs are N channel MOSFET.
 4. The power supply circuit of claim 1,wherein the transistor is a NPN type transistor; the third and fourthMOSFETs are N channel MOSFETs.
 5. The power supply circuit of claim 4,wherein when the switch turns off, the transistor base is capable ofreceiving a low voltage level power-good signal, and the input voltageof the first load is capable of being transmitted to the PWM controllerthrough the voltage feedback circuit.
 6. The power supply circuit ofclaim 4, wherein when the switch turns on, the transistor base iscapable of receiving a high voltage level power-good signal, and theinput voltages of the first and second loads are capable of beingtransmitted to the PWM controller through the voltage feedback circuit.7. A power supply circuit, comprising: a pulse width modulation (PWM)controller capable of outputting PWM control signals; a voltage outputcircuit capable of receiving the PWM control signals and outputtingworking voltage to a plurality of loads according to the received PWMcontrol signals; and a voltage feedback circuit electrically connectedto the PWM controller and the plurality of loads; wherein the voltagefeedback circuit comprises a switch element capable of receiving apower-good signal; the voltage feedback circuit is capable of detectingthe input voltages of a plurality of loads according to the power-goodsignal and outputting feedback signals to the PWM controller accordingto the detected input voltages; and the PWM controller is capable ofadjusting its PWM control signal outputs, according to the receivedfeedback signals, and adjusting working voltages to the plurality ofloads; wherein the PWM controller comprises a first drive terminal, aphase terminal and a second drive terminal; the voltage output circuitcomprises a first MOSFET and a second MOSFET; the first and second driveterminals are electrically connected to grids of the first and secondMOSFETs; a first MOSFET drain is capable of receiving a first voltage; asecond MOSFET source is grounded; a first MOSFET source and a secondMOSFET drain are electrically connected to output working voltages; andthe phase terminal is electrically connected to the first MOSFET sourceand the second MOSFET drain.
 8. The power supply circuit of claim 7,wherein the PWM controller further comprises a boot terminal; and theboot terminal is electrically connected to the phase terminal through acapacitor.
 9. The power supply circuit of claim 7, further comprising aswitch; the plurality of loads comprises a first load and a second load;the first MOSFET source and the second MOSFET drain are electricallyconnected and grounded by the first load; and the first MOSFET sourceand the second MOSFET drain are electrically connected and groundedthrough the switch and the second load that are connected in series. 10.The power supply circuit of claim 7, wherein the first and secondMOSFETs are N channel MOSFET.
 11. The power supply circuit of claim 9,wherein the PWM controller further comprises a feedback terminal; theswitch element is a transistor; the voltage feedback circuit furthercomprises a third MOSFET and a fourth MOSFET; a transistor base iscapable of receiving a power-good signal; a transistor source isgrounded; a transistor collector is capable of receiving a secondvoltage through a first resistor; the transistor collector iselectrically connected to a third MOSFET grid; a third MOSFET source isgrounded; a third MOSFET drain is capable of receiving the secondvoltage through a second resistor; the third MOSFET drain iselectrically connected to a fourth MOSFET grid; a fourth MOSFET sourceis grounded by the second load; a fourth MOSFET drain is grounded by thefirst load; and the fourth MOSFET drain is electrically connected to thefeedback terminal.
 12. The power supply circuit of claim 11, wherein thetransistor is a NPN type transistor; the third and fourth MOSFETs are Nchannel MOSFETs.
 13. The power supply circuit of claim 12, wherein whenthe switch turns off, the transistor base is capable of receiving a lowvoltage level power-good signal, and the input voltage of the first loadis capable of being transmitted to the PWM controller through thevoltage feedback circuit.
 14. The power supply circuit of claim 12,wherein when the switch turns on, the transistor base is capable ofreceiving a high voltage level power-good signal, and the input voltagesof the first and second loads are capable of being transmitted to thePWM controller through the voltage feedback circuit.